Locking device



Dec. 23, 1930. c. o. B. LOFGREN 1,786,352

LOCKING DEVICE Filed May 17, 192e IN1/MOR CARL O. B. LOFGRCN Patented Dec.l 23, 1930 UNITED STATES PATENr gori-ice CARL O. B, LOFGBEN, OF BRIDGEPORT, CONNECTICUT, .ASSIGNOR TO THE BRYANT ELEC- TRIC COMPANY, OF BBTDGEPGRT, CCNNECTICUT, A CORPORATTCN OF CONNECTICUT LOCKING nevica application fusa May 17,

This invention relates to locking devices for preventing the removal of certain electric fittings from the sockets in which they are In particular it has to do with threaded. a lock for a fuse safety device.

It has been found that many persons, instead of replacing fuses which have blown out, insert a coin orother piece of conducting metal into the fuse socket in place of the fuse, the coin bridging the space between the center and side contact pieces, thus completing the circuit. Then if a heavy current is sent through the circuit there is no fuse to blow out and the electricalrdevices in the circuit are subjected to heavier current than their design contemplated.

Safety devices have been provided which, when inserted in a fuse socket, make it impossible to bridge the contacts by a coin and difficult to insert anything except a fuse especially designed to lit the socket with the safety device in place.

The object of this invention is to provide a locking device for use with such safety devices, or in similar ttings, to prevent their removal from the sockets in whichthey are threaded.

Another object is to provide a locking device for such purposes which shall be simple, compact and economical. v

A further object is to provide a locking device which will engage the socket wall se-V curely regardless of slight irregularities in' the contour of the wall.

One embodiment of the invention is described hereinafter and is illustratedin the accompanying drawing.

In the drawings- Fig. 1 shows a sectional view of the safety device, taken on line 11 of Figure 2 with certain portions below the section removed;

Fig. 2 is a section on line 2-2 of Fig. 1;

Fig. 3 is an exploded view of the safety device;

Fig. 4 is a section on line 4-4 of Fig. 1;

Fig. 5 shows in detail the toothed end of a locking dog; f

Fig. 6 shows a Spanner key for'screwing the safety device in place.

The fuse safety device consists of a cir- 1928. Serial No. 278,527.

cular button 1 of insulating material having near the periphery on one face an annular wall 2 leaving a shoulder 3. The other face of this button is recessed to receive the locking mechanism. There is a main circular recess 4 leaving an annular rim 5 which has two apertures 6, 7 equidistant on the periphery. In register with these apertures and on opposite sides of the center are divergent transverse shallow recesses 8, 9, these recesses having their inner side walls parallel each to each, and their outer side Walls divergent from the inner walls. At the inner ends of these recesses are countersunk portions 10, 11. Extending between Irecesses 8, 9 at one side of the button is a crescent shaped recess 12 of less depth than the recesses 8, 9, the three recesses leaving a central transverse boss 13. 'y Through the center of the button is a circular opening 14.

For threading the device into the fuse socket, there is provided a screw thread shell 15 which surrounds the vbutton 1, one end being flanged to overlie the rim 5 and the other end being turned in over the shoulder 3 in any known manner. This shell is slotted opposite the apertures 6 and 7 and has inturned lugs, shown at 17, 18 in Figure 1, which extend into recesses in the rim 5 to prevent rotation of the shell about the button. The locking mechanism consists of two dogs 19, 2O of identical shape, stamped from thin metal. These dogs have off-setv ends 21, 22 which, when the dogs Aare placed in the recesses 8, 9, extend into the counter sunk portions 10, 11. These portions are of such size as to permit limited longitudinal movement of the dogs and so afford loose pivoting of the dogs on the button. The other ends of the dogs are serrated and extend through the apertures 6, 7 and the slots in the shell 15, the serrated or toothed ends'lying adjacent the periphery of the device.

Fig. 5 best shows the outer toothed end. It is to be noted that each tooth presents sloping face in the direction of desired rotation, indicated by the arrow, and a sharply inclined face in the reverse direction. By reason of the eccentric position of thepivot, the toothed end, in swinging to the dotted LOG the shell 15 but when swung over the divergent outer-walls of the the toothed ends protriule a ,suhl amount beyond the periphery of shell, l5. The reason for this is, of course,

that the toothed ends swing on an arc theY center ofwhich is not at the center of the button.

Each dog has a hole through it to receive an offset end of the spring 23 which is curved to lie in the recess l2 around the curved end ofthe boss 13. The tendency of the ends of the springs to 'separate causes the dogs tobe pushed against the divergentsides oftheir recesses, the ends 2l, 22 pivoting in the recesses, 10, 11, thus extending the toothed portions 24, 25 beyond the periphery of shell 15. It is noted that the direction of turning about the pivots, caused by the spring is the same as-the desired rotation of the body about its center. The spring` tends also to push thev dogs outward to the limit of extension permitted by the loose pivoting in recesses l0, ll.

- This slight permitted movement of the pivot compensates for any irregularities in the periphery of the shell 15 and pr'irtici'llarly for the fact that the socket shell is shaped to provide threads, and all portions of its periphery in any plane are not equidistant from the center. Y

To secure the mechanism in position, there is a disc Q6 of fibrous material which fits within the rim 5 and rests on the boss i3 and is liush. with the top of rim. Another larger disc 271 of fibrous material rests on the flange 1.6 of shell l5 which overlies the rim 5. A third, small disc 28 which may be of metal, rests on the disc 2'?. A rivet 29 having a clos-ed flanged end 30 extends from the under side of the button through the three discs and has its other end pressed over upon the discY 28 thus binding all the parts securely together. i

he button l is most easily made by molding. The metal parts consisting of the dogs, VIdie spring, the rivet and the screw shell are of simple shape and the cost of making them is slight. rllhe discs are cut from sheet matciial. it is seen therefore that the device accomplishes the object of simplicity and econoiny in the matter of manufacture. Moreover, it is compact since all the parts are flat and fit closely together.

The safety device is screwed into the usual fuse socket by means of a Spanner key 36v inserted in -spaced recesses 34., the dogs offeringno resistance to turning since the slopingflanks-of the teeth first meet thesocket wall j and the dogs-,are swung about their pivots against the inner wallsoftheir recessesinmea-eea which position the toothed ends are close to the periphery of the shell. If necessary, due to irregularity in the socket the dogs move inwardly in the recesses 10, l1 against the resilient effort of the spring. rl`he fuse is then screwed into place with its contact shell lying outside the annular insulating wall 2 and its center contact engaging the head 30 of rivet 29. lThe other end. of the rivet engages the center contact of the socket so that the rivet serves as a conductor between the fuse and socket contacts.

lf the fuse blows out, it may be removed and another one inserted. A coin or other article can not be used because of the wall 2. By properly relating the extent of wall 2 from the button l and the extent of the fuse shell and fuse center contact from the body of the fuse, theuse of any but a proper size of fuse may be prevented.

The safety device cannot be remove-d because if reverse rotation is attempted the slightly protruding toothed ends 24, 25, with the sharply `inclined face presented in the attempted direction of rotation, at once engage the walls ofthe socket shell and tend to swing the dogs about the pivoting ends 2l, 22 into position in which they extend even morebeyond the shellfl; that is, they are swung against the divergent walls of their recesses. Therefore in addition to affording frictional resistance to turning, the toothed ends bite into the relatively soft metal of the shell and afford a positive lock.

Modifications of this preferred embodiment will doubtless occur to others in the exercise of their skill in the artA or of their invent-ive faculties. The invention is not limited to theembodiment shown but comprehends all such modifications-as fall within the scope of the following claims.

I claiml. In a safety device for a fuse, a button, transverse, divergent, non-radial recesses in one face of the button, said recesses extending tothe periphery at spaced points thereabout, dogs pivoted in said recesses and having toothed ends adjacent the periphery, and a spring means engaging each dogfand urging it about its pivot in the direction of desired rotation of the device.

2. In a safety device for a fuse, a button, transverse, divergent, non-radial recesses iu one faceof the button, said recesses extending to the periphery at spaced points thereabout, dogs pivoted in. saidY recesses and having toothed ends adjacent the periphery, spring means engaging eachdog and urging it about its pivot in the direction of desired rotation of the deviceand a. cap member on said body for holding saiddogs and spring means in position.

3. In asafetydevicefor a fuse, abutton, transverse, divergent, non-radialfrecesses in one faceof the button, said recessesextending to the periphery at spaced points thereabout, dogs pivoted in said recesses and having toothed ends adjacent the periphery, spring means engaging each dog and urging it about its pivot in theV direction of desired rotation of the device and a cap member on said body for holding` said dogs and spring means in position, a conducting member eX- tending through said body and said cap member, securing said capon the body and affording center contacts on each side of the body. Y

4. In a safety device for a fuse, al body portion having a peripheral rim on one side thereof, transverse, divergent, non-radial recesses in one-face of the body portion, said recesses extending to the periphery at spaced points thereabout, said rim being apertured at said points, dogs pivoted in said recesses, and having toothed ends adjacent the periphery, a spring means engaging each dog and urging it about its pivot in the direction of desired rotation of the device, and a cap member on said body for h-olding said dogs and spring means in position. y

5. A safety device for a fuse comprising a button having socket engaging means thereon, an annular Wall on one side thereof spaced from the periphery, a peripheral rim on the other side, said other side having tWo divergent transverse recesses on opposite sides of the center and extending in opposite directions, With a curved connecting recess of less depth, said rim being apertured in register With said recesses, dogs pivoted in each transverse recess and extending adjacent the periphery of said body portion, the ends of the dogs being toothed, a curved spring lying in the connecting recess and engaging both dogs to urge them about their pivots in the direction of desired rotation of the body, a disc Within the rim land resting on said spring and dogs, a cap on said rim and a rivet eX- tending through the body and engaging said cap member, said rivet affording center contacts on each side of the body.

6. A locking mechanism for preventing reverse rotation of a circular body having a screw shell for threading into a socket, comprising a dog having a toothed end extending through a slot in the screw shell and adapted to bite on reverse rotation, said dog being pivotally mounted at an off-center part of the body and having limited freedom of non-pivotal movement whereby the position of its toothed end may vary, together with resilient means urging the toothed end of the dog outwardly and about its pivot in the direction of desired rotation.

In testimony whereof I have signed my name to this specification.

CARL O. B. LOFGREN. 

